EP0019520A1 - Envelope separators for electric accumulators and means for realizing their manufacture - Google Patents

Abstract

Separator obtained by bending a sheet of porous plastic material and by consecutive welding of the lateral edges, at (8), and in which the surface of the envelope has ribs (2), which (2) are interrupted at least near the zone of bending (4) of the sheet. <IMAGE>

Description

The present invention relates to envelope separators for electric accumulator plates and more specifically to separators of this type obtained by folding a sheet of suitable porous plastic material and subsequent welding on the sides, in which the inner or outer surface of the 'envelope has ribs with longitudinal development.

The invention also relates to means specially designed for manufacturing these separators.

As is known, the envelope separators, in addition to preventing contact between the plates of different polarity, have the function of enveloping the positive or negative plates of the accumulator in order to collect the sludge which forms at following the detachment of particles of active material and which could give rise to short-circuits.

These ribs have the role of keeping the plates sufficiently spaced apart so as to ensure, in particular for lead accumulators, the necessary availability of electrolyte around the plates. On the other hand, these ribs are produced along the length of the sheet, so as to define between them longitudinal channels which promote the exit of gases.

However, in known envelope separators, the longitudinal ribs are continuous, so that the folding of the sheets to obtain the envelope can cause tears or breaks in the folded area.

According to a well known manufacturing system, the envelope separators are obtained from sheets of porous plastic resistant to traction, such as polyolefins, provided with continuous ribs and by cold folding these same sheets, at the level of the zone. intended to constitute the bottom of the envelope, and then proceeding to the welding of the lateral edges.

Thanks to this same resistance, the materials used are not subject to ruptures or tears in the bending zone where the continuous ribs are present. There is however the disadvantage that these materials are expensive, not to mention that the process for manufacturing separators is quite complex given that one starts with solutions or emulsions of materials.

Another known system for obtaining envelope separators consists of sheets of sintered plastic material, provided with continuous ribs, and in heating, during the folding operation, the area concerned so as to eliminate, by softening, the rigidity caused by the ribs. This system makes it possible to use an economical material but nevertheless requires a reheating operation which makes the process of manufacturing the separators even more complicated.

The object of the present invention is to produce a shell separator, provided with ribs with longitudinal development, making it possible to use sheets of porous plastic material, even of the economic type, and which lends itself to being folded to form the bottom of the 'envelope without necessarily requiring special treatment to avoid breakage at the folding area.

According to the invention, this is obtained with an envelope separator using a porous plastic sheet on which the longitudinal ribs are inter broken at least at the bending zone.

According to a preferred embodiment, the ribs are in the form of series of ribs side by side, which series are separated from each other by a smooth space and are repeated with a constant pitch.

Advantageously, the interrupted ribs are obtained from a layer of powdered plastic material shaped by a forming roller and then sintered. The roller acts on the layer of material with a surface having a plurality of cavities whose characteristics correspond to those of the ribs which it is desired to obtain on the finished separator.

• la figure 1 montre une partie d'une feuille de matière plastique poreuse, présentant des nervures d'espacement selon l'invention ;
• la figure 2 est une vue partielle et en perspective d'un accumulateur électrique utilisant des séparateurs à enveloppe obtenus à partir de la feuille de la figure 1 ;
• la figure 3 montre, également en perspective, un rouleau qui permet de façonner les séries de nervures avec le matériau à l'état de poudre ;
• la figure 4 montre, d'une manière schématique, le procédé de formage des nervures en utilisant le rouleau de la figure 3.

The invention will now be described, by way of example only, with reference to the appended drawings, in which:

• FIG. 1 shows part of a sheet of porous plastic material, having spacing ribs according to the invention;
• Figure 2 is a partial perspective view of an electric accumulator using envelope separators obtained from the sheet of Figure 1;
• FIG. 3 shows, also in perspective, a roller which makes it possible to shape the series of ribs with the material in the powder state;
• FIG. 4 schematically shows the method of forming the ribs using the roller of FIG. 3.

In accordance with FIG. 1, the reference 1 indicates a portion of sheet or ribbon of economical porous plastic material, such as sintered polyvinyl chloride (PVC), having, on one side, the longitudi spacing ribs. nales 2 which, according to the invention, are interrupted.

These ribs are arranged side by side and parallel so as to form transverse series 3 of ribs, which repeat with a constant pitch over the entire length of the sheet 1.

The series 3 of ribs are separated from one another by free spaces or flat surfaces 4 which constitute the zones at the level of which the sheet can be folded, along the dotted axis 4 ', so as to form the bottom of the envelope separator.

Thanks to the absence of ribs at the level of the zones 4, the sheet folding operation is carried out on the thin part of the latter, without risk of breakage or tearing of the material, that is to say ..without this part having to be subjected to reheating or other particular treatments.

Once the sheet 1 has been folded, the side edges 5 turned over on themselves are closed to form the envelope separator as shown in FIG. 2.

This figure partially shows an electric accumulator in which separators with an envelope S are used folded at the level of the zone 4 devoid of ribs 2.

Each separator contains a negative plate 6, and consequently the ribs 2 are located outside the envelope so as to achieve the desired spacing with respect to the positive plate 7.

It is however obvious that the envelope may as well contain the positive plate, in which case the ribs will be inside.

The envelope separator is closed by welding, welding which in the figure is represented only on one side and which is indicated by 8.

As can be seen in the figure, each envelope separator rests with its bottom or folded part 4 on the bottom 9 of the accumulator tank.

The roller 10 of FIG. 3 makes it possible to obtain the spacing ribs when the material is in the powder state. This roller rotates around a fixed axis 11 and has on its cylindrical surface a plurality of cavities 12 whose characteristics (number, dimensions and arrangement) correspond to that of the ribs which it is desired to obtain on the finished separator.

Thus, if the ribs that we want to obtain are those shown in Figure 1, the cavities 12 are formed in an arc of a circle and are in the form of series of cavities arranged side by side and equidistant which are repeated periodically, as the series 3 of ribs in Figure 1.

As shown in Figure 4, during the formation of the ribs in the powder state the roller 10 is rotated and acts with a certain pressure on the layer of powder 13 of material while this same layer advances driven by the support 14 .

The layer of powder compressed with the ribs 2 ′ is then passed through an oven for sintering, and a sheet like that shown in FIG. 1 is thus obtained at the outlet.

As an economical material used, polyvinyl chloride (PVC) sintered has been cited by way of example, but it goes without saying that the invention applies to any other material present. both appropriate characteristics of porosity, resistance to the aggressive action of the electrolyte, etc.

Instead of starting from a material in the powder state as described, the envelope separator can also be obtained from a smooth sintered sheet which is passed between two suitably profiled rollers so as to produce, by stamping, the series of interrupted ribs.

The envelope separator can also be obtained from a pasty mass of plastic in the form of a solution or emulsion, formed between two rollers with suitable profiles depending on whether one wishes to obtain full or hollow interrupted ribs .

Whether in the case of a smooth sintered sheet or in that of a pasty mass, the material, to be shaped, must naturally be brought to the softening state, which can be done by reheating the rollers.

Although the drawings and the description refer to linear ribs perpendicular to the bottom of the envelope, it goes without saying that, depending on practical requirements, the configuration of the ribs may be different from that shown. For example, the interrupted ribs may have a slight inclination relative to the longitudinal axis.

Finally, although reference has been made to folding and lateral welding operations to obtain the envelope separator, apart from the plate, in reality, in a continuous production process, these operations are carried out after positioning the positive or negative plate.

In this way we have the advantage of obtaining a set plate-envelope-insulator as an independent unit.

It goes without saying that the invention is not limited to the embodiment which has just been described and illustrated, but that it is on the contrary liable to modifications and variants all coming within the scope of the claims which follow.

Claims (7)

1. Enclosure separator for electric accumulator plates, obtained by folding a sheet of suitable porous plastic material and by consecutive welding of the lateral edges, and in which the interior or exterior surface of the envelope has spacing ribs with longitudinal development, characterized in that the ribs are interrupted at least at the level of the folding zone of the sheet. 2. envelope separator according to claim 1, characterized in that the ribs are in the form of series of ribs arranged side by side, which series are separated from each other by a smooth space and are repeated with a not constant. 3. envelope separator according to any one of claims 1 and 2, characterized in that the ribs are obtained from a continuous layer of powdered plastic material shaped by a forming roller and then sintered. 4. envelope separator according to claims 1 and 2, characterized in that the ribs are obtained from a continuous smooth sheet of sintered material which is passed between rollers with suitable profiles, so as to achieve by stamping said series of interrupted ribs, the ribs being formed in the softening state of the sheet. 5. envelope separator according to claims 1 and 2, characterized in that the ribs are obtained from a pasty mass of plastic material shaped by rollers with suitable profiles, so as to obtain the series of interrupted ribs, solid or hollow, the ribs being formed in the state of softening of the pasty mass. 6. envelope separator according to any one of the preceding claims, characterized in that the operations of folding and lateral welding of the sheet of material provided with interrupted ribs are carried out after positioning of the plate. 7. Means for carrying out the manufacture of the separator as defined in claim 3, characterized in that they comprise a forming roller which has a fixed axis around which it can rotate, and which has a cylindrical surface , which has a plurality of interrupted cavities having dimensions and an arrangement which make it possible to form the series of interrupted ribs which it is desired to obtain on the finished separator, said cylindrical surface being intended to be applied, with a slight pressure, to the powder layer.

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